Collaborative Research: RAPID Assessment of 2013 Flood Sedimentation, Button Rock Reservoir, North St. Vrain Watershed, CO

这一合作快速项目将评估2013年9月极端事件发生后科罗拉多州中北部纽顿岩水库北圣弗拉恩分水岭的洪水沉积情况。此外，它将填补关于火灾和洪水造成的基于事件的沉积的知识空白，并利用自1950年修建水库以来的泥沙积累记录，将知识扩展到年度和十年尺度。沉积记录将介绍盆地平均侵蚀速率和沉积的趋势，以及天然或人工湖中碳储存的趋势，以及过去60年从单一、大型事件到流动的流动情景下北圣弗拉纳河的碳输出率。纽扣岩石水库提供了一个独特的环境来评估前缘地区非常高的、罕见的洪水的影响，因为(1)水库建造以来，水库运营商没有进行过有意的冲刷事件，(2)水库地层记录了不间断的三角洲沉积，(3)这是唯一一个在没有重大历史木材收获、水流调节或土地利用影响的盆地中，从大陆分水岭到山前的沉积物流量不受阻碍的航道上水库。该小组将在2013年12月至2014年3月期间在三角洲沉积物中收集四个岩心。将完成对水库暴露的三角洲和水下部分的探地雷达调查。再加上大坝前地形图的信息，这些岩芯和探地雷达调查的信息将限制泥沙淤积的体积和空间分布。将从三角洲岩心采集样本进行放射性碳分析，以限制沉积物堆积，并通过盆地平均侵蚀速率深入了解景观剥蚀情况。流域内的碳通量将根据三角洲沉积物中的有机碳含量来确定。流量和降水记录将与核心信息进行比较，以分析在基于事件和季节性驱动的情况下流入水库的泥沙通量的趋势。该项目将收集过去60年来洪水和火灾对科罗拉多州前沿山脉侵蚀的影响的独特、不间断和未受干扰的记录。它将有助于理解景观对这些重大事件的反应，以及这些事件在景观中储存点之间移动碳的作用。这项工作的近期成果将是对2013年9月天气事件移动的物质量的精确估计--这一事件迫使朗蒙特市政府清除Button Creek水库中相关的沉积物脉冲，以恢复水库容量。该项目介绍了研究生和本科生的培训经验，在两所大学的同事之间建立了新的合作，并将与管理前缘范围内的水和泥沙流动的实体共享信息。

This collaborative RAPID project will assess flood sedimentation in Button Rock Reservoir, North St. Vrain watershed in north-central Colorado following the September 2013 extreme event. In addition, it will fill knowledge gaps about event-based sedimentation from fires and floods, and expand knowledge to annual and decadal scales using a record of sediment accumulation since construction of the reservoir in 1950. The sedimentary record will inform on trends in basin-averaged erosion rates and sedimentation, as well as on trends in carbon storage in natural or artificial lakes, and on rates of carbon export from North St. Vrain Creek under flow scenarios from single, large events to flows over the past six decades. Button Rock Reservoir provides a unique setting to assess the effects of a very high magnitude, infrequent flood in the Front Range because (1) no intentional flushing events have been conducted by the reservoir operators since construction of the reservoir, (2) the reservoir stratigraphy chronicles uninterrupted delta deposition, and (3) this is the only on-channel reservoir with unimpeded, natural sediment flux from the Continental Divide to the mountain front in a basin with no significant historic timber harvests, flow regulation, or land use impacts. The team will collect four cores within the delta deposit during the December 2013 to March 2014 timeframe. A ground-penetrating radar survey will be completed of the exposed delta and subaqueous portions of the reservoir. Together with information from pre-dam topographic maps, information from these cores and the GPR survey will constrain the volume and spatial distribution of sediment deposition. Samples from the delta cores will be collected for radiocarbon analysis to constrain sediment accumulation and provide insight into landscape denudation through basin-averaged erosion rates. The carbon flux within the catchment will be determined from organic carbon content in delta sediments. Discharge and precipitation records will be compared with the core information to analyze trends in sediment flux into the reservoir in response to event-based and seasonal drivers.This project will collect a unique uniterrupted and undisturbed record of the impact of floods and fires on erosion in Colorado's Front Range over the past six decades. It will inform understanding of how the landscape responds to such major events and the role of these events in moving Carbon among storage points in the landscape. A near-term outcome of the work will be a refined estimate of the amount of material moved by the September 2013 weather event--an event that has necessitated the City of Longmont to remove the associated pulse of sediment from the Button Creek Reservoir in order to regain reservoir capacity. The project presents training experiences for graduate and undergraduate students, forges a new collaboration between colleagues at two universities, and will share information with entities that manage water and sediment flows along the Front Range.